Fertiliser-induced nitrous oxide emissions from vegetable production in the world and the regulating factors: A review

Abstract

The emission of nitrous oxide (N2O) from vegetable fields contributes to the global greenhouse gases budget. However, reliable estimation of N2O emissions from vegetable production in the word has been lack. Vegetable cropping systems are characterised with high N application rates, irrigation, intensive production and multiple planting-harvest cycles during the year. Improved understanding of the key factors controlling N2O production is critical for developing effective mitigation strategies for vegetable cropping systems under different climate, soil type and management practices. Based on a comprehensive literature review and data analysis, we estimated the global N2O emission from vegetable production using seasonal fertiliser-induced emission factors (EFs) and examined the relationship of the seasonal emissions and EFs to possible controlling factors. The global average seasonal EF for vegetable fields is around 0.94% of applied N fertiliser, which is very similar to the Intergovernmental Panel on Climate Change (IPCC) annual emission factor of 1.0% for all cropping systems. The total N2O emission from global vegetable production is estimated to be 9.5 × 107 kg N2O–N yr−1, accounting for 9.0% of the total N2O emissions from synthetic fertilisers. Stepwise multiple regression analysis on the relationships of soil properties, climatic factors and N application rates to seasonal N2O emissions and N2O EFs showed that N fertiliser application rate is the main regulator of seasonal N2O emission from vegetable fields but the seasonal EFs are negatively related to soil organic carbon (SOC) content. In fields receiving ≥250 kg ha−1 N fertiliser, 67% (n = 23, P ≤ 0.01) of the variation in seasonal emissions can be explained by the combined effects of N application rate, mean water-filled pore space (WFPS) and air temperature, while 59% (n = 23, P ≤ 0.01) of the variation in seasonal EFs relates to temperature, mean WFPS and soil pH. The result also shows that in vegetable fields with mean seasonal air temperature higher than 14 °C, increases in SOC decrease the seasonal EF and total N2O emissions from fertiliser N.